bitflipper
They should still be there. AFAIK, new SONAR installs do not delete anything. First, check to see if Pantheon and V-Vocal are still physically there. I don't have 8.5 anymore, but IIRC V-Vocal was under Shared DXi. Pantheon may have been in a subdirectory below vstplugins, but I don't recall.

So, the plugs I'm looking for are in the Cakewalk>Shared Plugins folder. Pantheon, classicphaser, AmpSim, all of that. V-Vocal has a folder under Shared DXi, and says Cronus.dll (?).

So why are they not showing up in 8.5? I tried copying the Pantheon dll to the VST folder, and rescanning... still nothing.

You could just try running the 8.5 installer again, and make sure that all of the plugin options are checked under advanced install setting.

Double check the plugin paths in 8.5 in case the SPLST install changed them. When you say "I tried copying the Pantheon dll to the VST folder" - that won't help if the folder isn't in the list of 8.5 paths.

Platinum screws up things in 8.53.
In particular, the plugin manager. This may be your problem.
If you roll back to the Dec 2016 version of Platinum, the PM seems to be OK.
 

have you tried rescanning your plug ins ?

As best I can tell the "missing" plug-ins are DX format.
 
DX plug-ins do not rely on users defining paths to their locations. DX plug-ins are registered during installation. Moving them to a VST folder will not help, in fact that will break the ability of SONAR to find them since SONAR relies on the information placed in the registry during installation.
 
Running the VST scanner will not help, it does not work with DX plug-ins.
 
While SONAR installers will update plug-ins and utilities, the installers do not remove them.
 
Since the plug-ins work in existing projects, this would suggest the plug-ins are installed correctly and SONAR can find them. It seems like the plug-ins are missing for the current layout. Is the plug-in layout set to "Default all plug-ins?"

Grudunza

If I open up old projects that used Lexicon or the other CW effects, they are still there and sound fine and can be exported and such. But any idea about why they are no longer showing up in 8.5 for me? Did one of the later installs (X3, Plat, etc.) make those things go away? I'm running 8.5 (64) on a Win7 machine.

As I said above, it's broken.
Platinum installs a new Plugin manager that overwrites 8.5's. This is a shared utility that 8.5 doesn't work correctly with.
 
8.5 projects will load with plugins intact. and plugs should be visible in the plugin manager and plugs 'should' work in projects using existing plugin layouts. But, any new plugins or plugin layouts created will not be available for new instances from within the project window in 8.5 (track view or console view). 
 
A possible semi-workaround, that I haven't tried yet, would be to uninstall all Cakewalk. Then, install 32 bit 8.5 and 64 bit Platinum. Each would then use their own Plugin manager. (Hypothetically.)
 
Yea, it sucks.

I have Platinum and I am able to use V-Vocal.  After I installed/upgraded to Platinum, I installed an older version of Sonar, probably the last version that still had it.  No problems here...

"run run run ....like Tom Cruise"